// Copied from https://raw.githubusercontent.com/mrdoob/three.js/dev/examples/jsm/loaders/GLTFLoader.js on 02.08.2021
// Modified by yandeu to work on node.js. Marked as MOD(yandeu).
// (Removed assignTexture and loadTexture)

import {
  AnimationClip,
  Bone,
  Box3,
  BufferAttribute,
  BufferGeometry,
  ClampToEdgeWrapping,
  Color,
  DirectionalLight,
  DoubleSide,
  FileLoader,
  FrontSide,
  Group,
  ImageBitmapLoader,
  InterleavedBuffer,
  InterleavedBufferAttribute,
  Interpolant,
  InterpolateDiscrete,
  InterpolateLinear,
  Line,
  LineBasicMaterial,
  LineLoop,
  LineSegments,
  LinearFilter,
  LinearMipmapLinearFilter,
  LinearMipmapNearestFilter,
  Loader,
  LoaderUtils,
  Material,
  MathUtils,
  Matrix4,
  Mesh,
  MeshBasicMaterial,
  MeshPhysicalMaterial,
  MeshStandardMaterial,
  MirroredRepeatWrapping,
  NearestFilter,
  NearestMipmapLinearFilter,
  NearestMipmapNearestFilter,
  NumberKeyframeTrack,
  Object3D,
  OrthographicCamera,
  PerspectiveCamera,
  PointLight,
  Points,
  PointsMaterial,
  PropertyBinding,
  QuaternionKeyframeTrack,
  RGBAFormat,
  RepeatWrapping,
  Skeleton,
  SkinnedMesh,
  Sphere,
  SpotLight,
  TangentSpaceNormalMap,
  Texture,
  TextureLoader,
  TriangleFanDrawMode,
  TriangleStripDrawMode,
  Vector2,
  Vector3,
  VectorKeyframeTrack
} from 'three'

class GLTFLoader extends Loader {
  constructor(manager) {
    super(manager)

    this.dracoLoader = null
    this.ktx2Loader = null
    this.meshoptDecoder = null

    this.pluginCallbacks = []

    this.register(function (parser) {
      return new GLTFMaterialsClearcoatExtension(parser)
    })

    this.register(function (parser) {
      return new GLTFTextureBasisUExtension(parser)
    })

    this.register(function (parser) {
      return new GLTFTextureWebPExtension(parser)
    })

    this.register(function (parser) {
      return new GLTFMaterialsTransmissionExtension(parser)
    })

    this.register(function (parser) {
      return new GLTFMaterialsVolumeExtension(parser)
    })

    this.register(function (parser) {
      return new GLTFMaterialsIorExtension(parser)
    })

    this.register(function (parser) {
      return new GLTFMaterialsSpecularExtension(parser)
    })

    this.register(function (parser) {
      return new GLTFLightsExtension(parser)
    })

    this.register(function (parser) {
      return new GLTFMeshoptCompression(parser)
    })
  }

  load(url, onLoad, onProgress, onError) {
    const scope = this

    let resourcePath

    if (this.resourcePath !== '') {
      resourcePath = this.resourcePath
    } else if (this.path !== '') {
      resourcePath = this.path
    } else {
      resourcePath = LoaderUtils.extractUrlBase(url)
    }

    // Tells the LoadingManager to track an extra item, which resolves after
    // the model is fully loaded. This means the count of items loaded will
    // be incorrect, but ensures manager.onLoad() does not fire early.
    this.manager.itemStart(url)

    const _onError = function (e) {
      if (onError) {
        onError(e)
      } else {
        console.error(e)
      }

      scope.manager.itemError(url)
      scope.manager.itemEnd(url)
    }

    const loader = new FileLoader(this.manager)

    loader.setPath(this.path)
    loader.setResponseType('arraybuffer')
    loader.setRequestHeader(this.requestHeader)
    loader.setWithCredentials(this.withCredentials)

    loader.load(
      url,
      function (data) {
        try {
          scope.parse(
            data,
            resourcePath,
            function (gltf) {
              onLoad(gltf)

              scope.manager.itemEnd(url)
            },
            _onError
          )
        } catch (e) {
          _onError(e)
        }
      },
      onProgress,
      _onError
    )
  }

  setDRACOLoader(dracoLoader) {
    this.dracoLoader = dracoLoader
    return this
  }

  setDDSLoader() {
    throw new Error('THREE.GLTFLoader: "MSFT_texture_dds" no longer supported. Please update to "KHR_texture_basisu".')
  }

  setKTX2Loader(ktx2Loader) {
    this.ktx2Loader = ktx2Loader
    return this
  }

  setMeshoptDecoder(meshoptDecoder) {
    this.meshoptDecoder = meshoptDecoder
    return this
  }

  register(callback) {
    if (this.pluginCallbacks.indexOf(callback) === -1) {
      this.pluginCallbacks.push(callback)
    }

    return this
  }

  unregister(callback) {
    if (this.pluginCallbacks.indexOf(callback) !== -1) {
      this.pluginCallbacks.splice(this.pluginCallbacks.indexOf(callback), 1)
    }

    return this
  }

  parse(data, path, onLoad, onError) {
    let content
    const extensions = {}
    const plugins = {}

    if (typeof data === 'string') {
      content = data
    } else {
      const magic = LoaderUtils.decodeText(new Uint8Array(data, 0, 4))

      if (magic === BINARY_EXTENSION_HEADER_MAGIC) {
        try {
          extensions[EXTENSIONS.KHR_BINARY_GLTF] = new GLTFBinaryExtension(data)
        } catch (error) {
          if (onError) onError(error)
          return
        }

        content = extensions[EXTENSIONS.KHR_BINARY_GLTF].content
      } else {
        content = LoaderUtils.decodeText(new Uint8Array(data))
      }
    }

    const json = JSON.parse(content)

    if (json.asset === undefined || json.asset.version[0] < 2) {
      if (onError) onError(new Error('THREE.GLTFLoader: Unsupported asset. glTF versions >=2.0 are supported.'))
      return
    }

    const parser = new GLTFParser(json, {
      path: path || this.resourcePath || '',
      crossOrigin: this.crossOrigin,
      requestHeader: this.requestHeader,
      manager: this.manager,
      ktx2Loader: this.ktx2Loader,
      meshoptDecoder: this.meshoptDecoder
    })

    parser.fileLoader.setRequestHeader(this.requestHeader)

    for (let i = 0; i < this.pluginCallbacks.length; i++) {
      const plugin = this.pluginCallbacks[i](parser)
      plugins[plugin.name] = plugin

      // Workaround to avoid determining as unknown extension
      // in addUnknownExtensionsToUserData().
      // Remove this workaround if we move all the existing
      // extension handlers to plugin system
      extensions[plugin.name] = true
    }

    if (json.extensionsUsed) {
      for (let i = 0; i < json.extensionsUsed.length; ++i) {
        const extensionName = json.extensionsUsed[i]
        const extensionsRequired = json.extensionsRequired || []

        switch (extensionName) {
          case EXTENSIONS.KHR_MATERIALS_UNLIT:
            extensions[extensionName] = new GLTFMaterialsUnlitExtension()
            break

          case EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS:
            extensions[extensionName] = new GLTFMaterialsPbrSpecularGlossinessExtension()
            break

          case EXTENSIONS.KHR_DRACO_MESH_COMPRESSION:
            extensions[extensionName] = new GLTFDracoMeshCompressionExtension(json, this.dracoLoader)
            break

          case EXTENSIONS.KHR_TEXTURE_TRANSFORM:
            extensions[extensionName] = new GLTFTextureTransformExtension()
            break

          case EXTENSIONS.KHR_MESH_QUANTIZATION:
            extensions[extensionName] = new GLTFMeshQuantizationExtension()
            break

          default:
            if (extensionsRequired.indexOf(extensionName) >= 0 && plugins[extensionName] === undefined) {
              console.warn('THREE.GLTFLoader: Unknown extension "' + extensionName + '".')
            }
        }
      }
    }

    parser.setExtensions(extensions)
    parser.setPlugins(plugins)
    parser.parse(onLoad, onError)
  }
}

/* GLTFREGISTRY */

function GLTFRegistry() {
  let objects = {}

  return {
    get: function (key) {
      return objects[key]
    },

    add: function (key, object) {
      objects[key] = object
    },

    remove: function (key) {
      delete objects[key]
    },

    removeAll: function () {
      objects = {}
    }
  }
}

/*********************************/
/********** EXTENSIONS ***********/
/*********************************/

const EXTENSIONS = {
  KHR_BINARY_GLTF: 'KHR_binary_glTF',
  KHR_DRACO_MESH_COMPRESSION: 'KHR_draco_mesh_compression',
  KHR_LIGHTS_PUNCTUAL: 'KHR_lights_punctual',
  KHR_MATERIALS_CLEARCOAT: 'KHR_materials_clearcoat',
  KHR_MATERIALS_IOR: 'KHR_materials_ior',
  KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS: 'KHR_materials_pbrSpecularGlossiness',
  KHR_MATERIALS_SPECULAR: 'KHR_materials_specular',
  KHR_MATERIALS_TRANSMISSION: 'KHR_materials_transmission',
  KHR_MATERIALS_UNLIT: 'KHR_materials_unlit',
  KHR_MATERIALS_VOLUME: 'KHR_materials_volume',
  KHR_TEXTURE_BASISU: 'KHR_texture_basisu',
  KHR_TEXTURE_TRANSFORM: 'KHR_texture_transform',
  KHR_MESH_QUANTIZATION: 'KHR_mesh_quantization',
  EXT_TEXTURE_WEBP: 'EXT_texture_webp',
  EXT_MESHOPT_COMPRESSION: 'EXT_meshopt_compression'
}

/**
 * Punctual Lights Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_lights_punctual
 */
class GLTFLightsExtension {
  constructor(parser) {
    this.parser = parser
    this.name = EXTENSIONS.KHR_LIGHTS_PUNCTUAL

    // Object3D instance caches
    this.cache = { refs: {}, uses: {} }
  }

  _markDefs() {
    const parser = this.parser
    const nodeDefs = this.parser.json.nodes || []

    for (let nodeIndex = 0, nodeLength = nodeDefs.length; nodeIndex < nodeLength; nodeIndex++) {
      const nodeDef = nodeDefs[nodeIndex]

      if (nodeDef.extensions && nodeDef.extensions[this.name] && nodeDef.extensions[this.name].light !== undefined) {
        parser._addNodeRef(this.cache, nodeDef.extensions[this.name].light)
      }
    }
  }

  _loadLight(lightIndex) {
    const parser = this.parser
    const cacheKey = 'light:' + lightIndex
    let dependency = parser.cache.get(cacheKey)

    if (dependency) return dependency

    const json = parser.json
    const extensions = (json.extensions && json.extensions[this.name]) || {}
    const lightDefs = extensions.lights || []
    const lightDef = lightDefs[lightIndex]
    let lightNode

    const color = new Color(0xffffff)

    if (lightDef.color !== undefined) color.fromArray(lightDef.color)

    const range = lightDef.range !== undefined ? lightDef.range : 0

    switch (lightDef.type) {
      case 'directional':
        lightNode = new DirectionalLight(color)
        lightNode.target.position.set(0, 0, -1)
        lightNode.add(lightNode.target)
        break

      case 'point':
        lightNode = new PointLight(color)
        lightNode.distance = range
        break

      case 'spot':
        lightNode = new SpotLight(color)
        lightNode.distance = range
        // Handle spotlight properties.
        lightDef.spot = lightDef.spot || {}
        lightDef.spot.innerConeAngle = lightDef.spot.innerConeAngle !== undefined ? lightDef.spot.innerConeAngle : 0
        lightDef.spot.outerConeAngle =
          lightDef.spot.outerConeAngle !== undefined ? lightDef.spot.outerConeAngle : Math.PI / 4.0
        lightNode.angle = lightDef.spot.outerConeAngle
        lightNode.penumbra = 1.0 - lightDef.spot.innerConeAngle / lightDef.spot.outerConeAngle
        lightNode.target.position.set(0, 0, -1)
        lightNode.add(lightNode.target)
        break

      default:
        throw new Error('THREE.GLTFLoader: Unexpected light type: ' + lightDef.type)
    }

    // Some lights (e.g. spot) default to a position other than the origin. Reset the position
    // here, because node-level parsing will only override position if explicitly specified.
    lightNode.position.set(0, 0, 0)

    lightNode.decay = 2

    if (lightDef.intensity !== undefined) lightNode.intensity = lightDef.intensity

    lightNode.name = parser.createUniqueName(lightDef.name || 'light_' + lightIndex)

    dependency = Promise.resolve(lightNode)

    parser.cache.add(cacheKey, dependency)

    return dependency
  }

  createNodeAttachment(nodeIndex) {
    const self = this
    const parser = this.parser
    const json = parser.json
    const nodeDef = json.nodes[nodeIndex]
    const lightDef = (nodeDef.extensions && nodeDef.extensions[this.name]) || {}
    const lightIndex = lightDef.light

    if (lightIndex === undefined) return null

    return this._loadLight(lightIndex).then(function (light) {
      return parser._getNodeRef(self.cache, lightIndex, light)
    })
  }
}

/**
 * Unlit Materials Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_unlit
 */
class GLTFMaterialsUnlitExtension {
  constructor() {
    this.name = EXTENSIONS.KHR_MATERIALS_UNLIT
  }

  getMaterialType() {
    return MeshBasicMaterial
  }

  extendParams(materialParams, materialDef, parser) {
    const pending = []

    materialParams.color = new Color(1.0, 1.0, 1.0)
    materialParams.opacity = 1.0

    const metallicRoughness = materialDef.pbrMetallicRoughness

    if (metallicRoughness) {
      if (Array.isArray(metallicRoughness.baseColorFactor)) {
        const array = metallicRoughness.baseColorFactor

        materialParams.color.fromArray(array)
        materialParams.opacity = array[3]
      }

      if (metallicRoughness.baseColorTexture !== undefined) {
        pending.push(parser.assignTexture(materialParams, 'map', metallicRoughness.baseColorTexture))
      }
    }

    return Promise.all(pending)
  }
}

/**
 * Clearcoat Materials Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_clearcoat
 */
class GLTFMaterialsClearcoatExtension {
  constructor(parser) {
    this.parser = parser
    this.name = EXTENSIONS.KHR_MATERIALS_CLEARCOAT
  }

  getMaterialType(materialIndex) {
    const parser = this.parser
    const materialDef = parser.json.materials[materialIndex]

    if (!materialDef.extensions || !materialDef.extensions[this.name]) return null

    return MeshPhysicalMaterial
  }

  extendMaterialParams(materialIndex, materialParams) {
    const parser = this.parser
    const materialDef = parser.json.materials[materialIndex]

    if (!materialDef.extensions || !materialDef.extensions[this.name]) {
      return Promise.resolve()
    }

    const pending = []

    const extension = materialDef.extensions[this.name]

    if (extension.clearcoatFactor !== undefined) {
      materialParams.clearcoat = extension.clearcoatFactor
    }

    if (extension.clearcoatTexture !== undefined) {
      pending.push(parser.assignTexture(materialParams, 'clearcoatMap', extension.clearcoatTexture))
    }

    if (extension.clearcoatRoughnessFactor !== undefined) {
      materialParams.clearcoatRoughness = extension.clearcoatRoughnessFactor
    }

    if (extension.clearcoatRoughnessTexture !== undefined) {
      pending.push(parser.assignTexture(materialParams, 'clearcoatRoughnessMap', extension.clearcoatRoughnessTexture))
    }

    if (extension.clearcoatNormalTexture !== undefined) {
      pending.push(parser.assignTexture(materialParams, 'clearcoatNormalMap', extension.clearcoatNormalTexture))

      if (extension.clearcoatNormalTexture.scale !== undefined) {
        const scale = extension.clearcoatNormalTexture.scale

        // https://github.com/mrdoob/three.js/issues/11438#issuecomment-507003995
        materialParams.clearcoatNormalScale = new Vector2(scale, -scale)
      }
    }

    return Promise.all(pending)
  }
}

/**
 * Transmission Materials Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_transmission
 * Draft: https://github.com/KhronosGroup/glTF/pull/1698
 */
class GLTFMaterialsTransmissionExtension {
  constructor(parser) {
    this.parser = parser
    this.name = EXTENSIONS.KHR_MATERIALS_TRANSMISSION
  }

  getMaterialType(materialIndex) {
    const parser = this.parser
    const materialDef = parser.json.materials[materialIndex]

    if (!materialDef.extensions || !materialDef.extensions[this.name]) return null

    return MeshPhysicalMaterial
  }

  extendMaterialParams(materialIndex, materialParams) {
    const parser = this.parser
    const materialDef = parser.json.materials[materialIndex]

    if (!materialDef.extensions || !materialDef.extensions[this.name]) {
      return Promise.resolve()
    }

    const pending = []

    const extension = materialDef.extensions[this.name]

    if (extension.transmissionFactor !== undefined) {
      materialParams.transmission = extension.transmissionFactor
    }

    if (extension.transmissionTexture !== undefined) {
      pending.push(parser.assignTexture(materialParams, 'transmissionMap', extension.transmissionTexture))
    }

    return Promise.all(pending)
  }
}

/**
 * Materials Volume Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_volume
 */
class GLTFMaterialsVolumeExtension {
  constructor(parser) {
    this.parser = parser
    this.name = EXTENSIONS.KHR_MATERIALS_VOLUME
  }

  getMaterialType(materialIndex) {
    const parser = this.parser
    const materialDef = parser.json.materials[materialIndex]

    if (!materialDef.extensions || !materialDef.extensions[this.name]) return null

    return MeshPhysicalMaterial
  }

  extendMaterialParams(materialIndex, materialParams) {
    const parser = this.parser
    const materialDef = parser.json.materials[materialIndex]

    if (!materialDef.extensions || !materialDef.extensions[this.name]) {
      return Promise.resolve()
    }

    const pending = []

    const extension = materialDef.extensions[this.name]

    materialParams.thickness = extension.thicknessFactor !== undefined ? extension.thicknessFactor : 0

    if (extension.thicknessTexture !== undefined) {
      pending.push(parser.assignTexture(materialParams, 'thicknessMap', extension.thicknessTexture))
    }

    materialParams.attenuationDistance = extension.attenuationDistance || 0

    const colorArray = extension.attenuationColor || [1, 1, 1]
    materialParams.attenuationTint = new Color(colorArray[0], colorArray[1], colorArray[2])

    return Promise.all(pending)
  }
}

/**
 * Materials ior Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_ior
 */
class GLTFMaterialsIorExtension {
  constructor(parser) {
    this.parser = parser
    this.name = EXTENSIONS.KHR_MATERIALS_IOR
  }

  getMaterialType(materialIndex) {
    const parser = this.parser
    const materialDef = parser.json.materials[materialIndex]

    if (!materialDef.extensions || !materialDef.extensions[this.name]) return null

    return MeshPhysicalMaterial
  }

  extendMaterialParams(materialIndex, materialParams) {
    const parser = this.parser
    const materialDef = parser.json.materials[materialIndex]

    if (!materialDef.extensions || !materialDef.extensions[this.name]) {
      return Promise.resolve()
    }

    const extension = materialDef.extensions[this.name]

    materialParams.ior = extension.ior !== undefined ? extension.ior : 1.5

    return Promise.resolve()
  }
}

/**
 * Materials specular Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_specular
 */
class GLTFMaterialsSpecularExtension {
  constructor(parser) {
    this.parser = parser
    this.name = EXTENSIONS.KHR_MATERIALS_SPECULAR
  }

  getMaterialType(materialIndex) {
    const parser = this.parser
    const materialDef = parser.json.materials[materialIndex]

    if (!materialDef.extensions || !materialDef.extensions[this.name]) return null

    return MeshPhysicalMaterial
  }

  extendMaterialParams(materialIndex, materialParams) {
    const parser = this.parser
    const materialDef = parser.json.materials[materialIndex]

    if (!materialDef.extensions || !materialDef.extensions[this.name]) {
      return Promise.resolve()
    }

    const pending = []

    const extension = materialDef.extensions[this.name]

    materialParams.specularIntensity = extension.specularFactor !== undefined ? extension.specularFactor : 1.0

    if (extension.specularTexture !== undefined) {
      pending.push(parser.assignTexture(materialParams, 'specularIntensityMap', extension.specularTexture))
    }

    const colorArray = extension.specularColorFactor || [1, 1, 1]
    materialParams.specularTint = new Color(colorArray[0], colorArray[1], colorArray[2])

    if (extension.specularColorTexture !== undefined) {
      pending.push(
        parser
          .assignTexture(materialParams, 'specularTintMap', extension.specularColorTexture)
          .then(function (texture) {
            // texture.encoding = sRGBEncoding
          })
      )
    }

    return Promise.all(pending)
  }
}

/**
 * BasisU Texture Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_texture_basisu
 */
class GLTFTextureBasisUExtension {
  constructor(parser) {
    this.parser = parser
    this.name = EXTENSIONS.KHR_TEXTURE_BASISU
  }

  loadTexture(textureIndex) {
    return // MOD(yandeu)
    const parser = this.parser
    const json = parser.json

    const textureDef = json.textures[textureIndex]

    if (!textureDef.extensions || !textureDef.extensions[this.name]) {
      return null
    }

    const extension = textureDef.extensions[this.name]
    const source = json.images[extension.source]
    const loader = parser.options.ktx2Loader

    if (!loader) {
      if (json.extensionsRequired && json.extensionsRequired.indexOf(this.name) >= 0) {
        throw new Error('THREE.GLTFLoader: setKTX2Loader must be called before loading KTX2 textures')
      } else {
        // Assumes that the extension is optional and that a fallback texture is present
        return null
      }
    }

    return parser.loadTextureImage(textureIndex, source, loader)
  }
}

/**
 * WebP Texture Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/EXT_texture_webp
 */
class GLTFTextureWebPExtension {
  constructor(parser) {
    this.parser = parser
    this.name = EXTENSIONS.EXT_TEXTURE_WEBP
    this.isSupported = null
  }

  loadTexture(textureIndex) {
    return // MOD(yandeu)
    const name = this.name
    const parser = this.parser
    const json = parser.json

    const textureDef = json.textures[textureIndex]

    if (!textureDef.extensions || !textureDef.extensions[name]) {
      return null
    }

    const extension = textureDef.extensions[name]
    const source = json.images[extension.source]

    let loader = parser.textureLoader
    if (source.uri) {
      const handler = parser.options.manager.getHandler(source.uri)
      if (handler !== null) loader = handler
    }

    return this.detectSupport().then(function (isSupported) {
      if (isSupported) return parser.loadTextureImage(textureIndex, source, loader)

      if (json.extensionsRequired && json.extensionsRequired.indexOf(name) >= 0) {
        throw new Error('THREE.GLTFLoader: WebP required by asset but unsupported.')
      }

      // Fall back to PNG or JPEG.
      return parser.loadTexture(textureIndex)
    })
  }

  detectSupport() {
    if (!this.isSupported) {
      this.isSupported = new Promise(function (resolve) {
        const image = new Image()

        // Lossy test image. Support for lossy images doesn't guarantee support for all
        // WebP images, unfortunately.
        image.src = ''

        image.onload = image.onerror = function () {
          resolve(image.height === 1)
        }
      })
    }

    return this.isSupported
  }
}

/**
 * meshopt BufferView Compression Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/EXT_meshopt_compression
 */
class GLTFMeshoptCompression {
  constructor(parser) {
    this.name = EXTENSIONS.EXT_MESHOPT_COMPRESSION
    this.parser = parser
  }

  loadBufferView(index) {
    const json = this.parser.json
    const bufferView = json.bufferViews[index]

    if (bufferView.extensions && bufferView.extensions[this.name]) {
      const extensionDef = bufferView.extensions[this.name]

      const buffer = this.parser.getDependency('buffer', extensionDef.buffer)
      const decoder = this.parser.options.meshoptDecoder

      if (!decoder || !decoder.supported) {
        if (json.extensionsRequired && json.extensionsRequired.indexOf(this.name) >= 0) {
          throw new Error('THREE.GLTFLoader: setMeshoptDecoder must be called before loading compressed files')
        } else {
          // Assumes that the extension is optional and that fallback buffer data is present
          return null
        }
      }

      return Promise.all([buffer, decoder.ready]).then(function (res) {
        const byteOffset = extensionDef.byteOffset || 0
        const byteLength = extensionDef.byteLength || 0

        const count = extensionDef.count
        const stride = extensionDef.byteStride

        const result = new ArrayBuffer(count * stride)
        const source = new Uint8Array(res[0], byteOffset, byteLength)

        decoder.decodeGltfBuffer(new Uint8Array(result), count, stride, source, extensionDef.mode, extensionDef.filter)
        return result
      })
    } else {
      return null
    }
  }
}

/* BINARY EXTENSION */
const BINARY_EXTENSION_HEADER_MAGIC = 'glTF'
const BINARY_EXTENSION_HEADER_LENGTH = 12
const BINARY_EXTENSION_CHUNK_TYPES = { JSON: 0x4e4f534a, BIN: 0x004e4942 }

class GLTFBinaryExtension {
  constructor(data) {
    this.name = EXTENSIONS.KHR_BINARY_GLTF
    this.content = null
    this.body = null

    const headerView = new DataView(data, 0, BINARY_EXTENSION_HEADER_LENGTH)

    this.header = {
      magic: LoaderUtils.decodeText(new Uint8Array(data.slice(0, 4))),
      version: headerView.getUint32(4, true),
      length: headerView.getUint32(8, true)
    }

    if (this.header.magic !== BINARY_EXTENSION_HEADER_MAGIC) {
      throw new Error('THREE.GLTFLoader: Unsupported glTF-Binary header.')
    } else if (this.header.version < 2.0) {
      throw new Error('THREE.GLTFLoader: Legacy binary file detected.')
    }

    const chunkContentsLength = this.header.length - BINARY_EXTENSION_HEADER_LENGTH
    const chunkView = new DataView(data, BINARY_EXTENSION_HEADER_LENGTH)
    let chunkIndex = 0

    while (chunkIndex < chunkContentsLength) {
      const chunkLength = chunkView.getUint32(chunkIndex, true)
      chunkIndex += 4

      const chunkType = chunkView.getUint32(chunkIndex, true)
      chunkIndex += 4

      if (chunkType === BINARY_EXTENSION_CHUNK_TYPES.JSON) {
        const contentArray = new Uint8Array(data, BINARY_EXTENSION_HEADER_LENGTH + chunkIndex, chunkLength)
        this.content = LoaderUtils.decodeText(contentArray)
      } else if (chunkType === BINARY_EXTENSION_CHUNK_TYPES.BIN) {
        const byteOffset = BINARY_EXTENSION_HEADER_LENGTH + chunkIndex
        this.body = data.slice(byteOffset, byteOffset + chunkLength)
      }

      // Clients must ignore chunks with unknown types.

      chunkIndex += chunkLength
    }

    if (this.content === null) {
      throw new Error('THREE.GLTFLoader: JSON content not found.')
    }
  }
}

/**
 * DRACO Mesh Compression Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_draco_mesh_compression
 */
class GLTFDracoMeshCompressionExtension {
  constructor(json, dracoLoader) {
    if (!dracoLoader) {
      throw new Error('THREE.GLTFLoader: No DRACOLoader instance provided.')
    }

    this.name = EXTENSIONS.KHR_DRACO_MESH_COMPRESSION
    this.json = json
    this.dracoLoader = dracoLoader
    this.dracoLoader.preload()
  }

  decodePrimitive(primitive, parser) {
    const json = this.json
    const dracoLoader = this.dracoLoader
    const bufferViewIndex = primitive.extensions[this.name].bufferView
    const gltfAttributeMap = primitive.extensions[this.name].attributes
    const threeAttributeMap = {}
    const attributeNormalizedMap = {}
    const attributeTypeMap = {}

    for (const attributeName in gltfAttributeMap) {
      const threeAttributeName = ATTRIBUTES[attributeName] || attributeName.toLowerCase()

      threeAttributeMap[threeAttributeName] = gltfAttributeMap[attributeName]
    }

    for (const attributeName in primitive.attributes) {
      const threeAttributeName = ATTRIBUTES[attributeName] || attributeName.toLowerCase()

      if (gltfAttributeMap[attributeName] !== undefined) {
        const accessorDef = json.accessors[primitive.attributes[attributeName]]
        const componentType = WEBGL_COMPONENT_TYPES[accessorDef.componentType]

        attributeTypeMap[threeAttributeName] = componentType
        attributeNormalizedMap[threeAttributeName] = accessorDef.normalized === true
      }
    }

    return parser.getDependency('bufferView', bufferViewIndex).then(function (bufferView) {
      return new Promise(function (resolve) {
        dracoLoader.decodeDracoFile(
          bufferView,
          function (geometry) {
            for (const attributeName in geometry.attributes) {
              const attribute = geometry.attributes[attributeName]
              const normalized = attributeNormalizedMap[attributeName]

              if (normalized !== undefined) attribute.normalized = normalized
            }

            resolve(geometry)
          },
          threeAttributeMap,
          attributeTypeMap
        )
      })
    })
  }
}

/**
 * Texture Transform Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_texture_transform
 */
class GLTFTextureTransformExtension {
  constructor() {
    this.name = EXTENSIONS.KHR_TEXTURE_TRANSFORM
  }

  extendTexture(texture, transform) {
    if (transform.texCoord !== undefined) {
      console.warn('THREE.GLTFLoader: Custom UV sets in "' + this.name + '" extension not yet supported.')
    }

    if (transform.offset === undefined && transform.rotation === undefined && transform.scale === undefined) {
      // See https://github.com/mrdoob/three.js/issues/21819.
      return texture
    }

    texture = texture.clone()

    if (transform.offset !== undefined) {
      texture.offset.fromArray(transform.offset)
    }

    if (transform.rotation !== undefined) {
      texture.rotation = transform.rotation
    }

    if (transform.scale !== undefined) {
      texture.repeat.fromArray(transform.scale)
    }

    texture.needsUpdate = true

    return texture
  }
}

/**
 * Specular-Glossiness Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_pbrSpecularGlossiness
 */

/**
 * A sub class of StandardMaterial with some of the functionality
 * changed via the `onBeforeCompile` callback
 * @pailhead
 */
class GLTFMeshStandardSGMaterial extends MeshStandardMaterial {
  constructor(params) {
    super()

    this.isGLTFSpecularGlossinessMaterial = true

    //various chunks that need replacing
    const specularMapParsFragmentChunk = ['#ifdef USE_SPECULARMAP', '	uniform sampler2D specularMap;', '#endif'].join(
      '\n'
    )

    const glossinessMapParsFragmentChunk = [
      '#ifdef USE_GLOSSINESSMAP',
      '	uniform sampler2D glossinessMap;',
      '#endif'
    ].join('\n')

    const specularMapFragmentChunk = [
      'vec3 specularFactor = specular;',
      '#ifdef USE_SPECULARMAP',
      '	vec4 texelSpecular = texture2D( specularMap, vUv );',
      '	texelSpecular = sRGBToLinear( texelSpecular );',
      '	// reads channel RGB, compatible with a glTF Specular-Glossiness (RGBA) texture',
      '	specularFactor *= texelSpecular.rgb;',
      '#endif'
    ].join('\n')

    const glossinessMapFragmentChunk = [
      'float glossinessFactor = glossiness;',
      '#ifdef USE_GLOSSINESSMAP',
      '	vec4 texelGlossiness = texture2D( glossinessMap, vUv );',
      '	// reads channel A, compatible with a glTF Specular-Glossiness (RGBA) texture',
      '	glossinessFactor *= texelGlossiness.a;',
      '#endif'
    ].join('\n')

    const lightPhysicalFragmentChunk = [
      'PhysicalMaterial material;',
      'material.diffuseColor = diffuseColor.rgb * ( 1. - max( specularFactor.r, max( specularFactor.g, specularFactor.b ) ) );',
      'vec3 dxy = max( abs( dFdx( geometryNormal ) ), abs( dFdy( geometryNormal ) ) );',
      'float geometryRoughness = max( max( dxy.x, dxy.y ), dxy.z );',
      'material.specularRoughness = max( 1.0 - glossinessFactor, 0.0525 ); // 0.0525 corresponds to the base mip of a 256 cubemap.',
      'material.specularRoughness += geometryRoughness;',
      'material.specularRoughness = min( material.specularRoughness, 1.0 );',
      'material.specularColor = specularFactor;'
    ].join('\n')

    const uniforms = {
      specular: { value: new Color().setHex(0xffffff) },
      glossiness: { value: 1 },
      specularMap: { value: null },
      glossinessMap: { value: null }
    }

    this._extraUniforms = uniforms

    this.onBeforeCompile = function (shader) {
      for (const uniformName in uniforms) {
        shader.uniforms[uniformName] = uniforms[uniformName]
      }

      shader.fragmentShader = shader.fragmentShader
        .replace('uniform float roughness;', 'uniform vec3 specular;')
        .replace('uniform float metalness;', 'uniform float glossiness;')
        .replace('#include <roughnessmap_pars_fragment>', specularMapParsFragmentChunk)
        .replace('#include <metalnessmap_pars_fragment>', glossinessMapParsFragmentChunk)
        .replace('#include <roughnessmap_fragment>', specularMapFragmentChunk)
        .replace('#include <metalnessmap_fragment>', glossinessMapFragmentChunk)
        .replace('#include <lights_physical_fragment>', lightPhysicalFragmentChunk)
    }

    Object.defineProperties(this, {
      specular: {
        get: function () {
          return uniforms.specular.value
        },
        set: function (v) {
          uniforms.specular.value = v
        }
      },

      specularMap: {
        get: function () {
          return uniforms.specularMap.value
        },
        set: function (v) {
          uniforms.specularMap.value = v

          if (v) {
            this.defines.USE_SPECULARMAP = '' // USE_UV is set by the renderer for specular maps
          } else {
            delete this.defines.USE_SPECULARMAP
          }
        }
      },

      glossiness: {
        get: function () {
          return uniforms.glossiness.value
        },
        set: function (v) {
          uniforms.glossiness.value = v
        }
      },

      glossinessMap: {
        get: function () {
          return uniforms.glossinessMap.value
        },
        set: function (v) {
          uniforms.glossinessMap.value = v

          if (v) {
            this.defines.USE_GLOSSINESSMAP = ''
            this.defines.USE_UV = ''
          } else {
            delete this.defines.USE_GLOSSINESSMAP
            delete this.defines.USE_UV
          }
        }
      }
    })

    delete this.metalness
    delete this.roughness
    delete this.metalnessMap
    delete this.roughnessMap

    this.setValues(params)
  }

  copy(source) {
    super.copy(source)

    this.specularMap = source.specularMap
    this.specular.copy(source.specular)
    this.glossinessMap = source.glossinessMap
    this.glossiness = source.glossiness
    delete this.metalness
    delete this.roughness
    delete this.metalnessMap
    delete this.roughnessMap
    return this
  }
}

class GLTFMaterialsPbrSpecularGlossinessExtension {
  constructor() {
    this.name = EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS

    this.specularGlossinessParams = [
      'color',
      'map',
      'lightMap',
      'lightMapIntensity',
      'aoMap',
      'aoMapIntensity',
      'emissive',
      'emissiveIntensity',
      'emissiveMap',
      'bumpMap',
      'bumpScale',
      'normalMap',
      'normalMapType',
      'displacementMap',
      'displacementScale',
      'displacementBias',
      'specularMap',
      'specular',
      'glossinessMap',
      'glossiness',
      'alphaMap',
      'envMap',
      'envMapIntensity',
      'refractionRatio'
    ]
  }

  getMaterialType() {
    return GLTFMeshStandardSGMaterial
  }

  extendParams(materialParams, materialDef, parser) {
    const pbrSpecularGlossiness = materialDef.extensions[this.name]

    materialParams.color = new Color(1.0, 1.0, 1.0)
    materialParams.opacity = 1.0

    const pending = []

    if (Array.isArray(pbrSpecularGlossiness.diffuseFactor)) {
      const array = pbrSpecularGlossiness.diffuseFactor

      materialParams.color.fromArray(array)
      materialParams.opacity = array[3]
    }

    if (pbrSpecularGlossiness.diffuseTexture !== undefined) {
      pending.push(parser.assignTexture(materialParams, 'map', pbrSpecularGlossiness.diffuseTexture))
    }

    materialParams.emissive = new Color(0.0, 0.0, 0.0)
    materialParams.glossiness =
      pbrSpecularGlossiness.glossinessFactor !== undefined ? pbrSpecularGlossiness.glossinessFactor : 1.0
    materialParams.specular = new Color(1.0, 1.0, 1.0)

    if (Array.isArray(pbrSpecularGlossiness.specularFactor)) {
      materialParams.specular.fromArray(pbrSpecularGlossiness.specularFactor)
    }

    if (pbrSpecularGlossiness.specularGlossinessTexture !== undefined) {
      const specGlossMapDef = pbrSpecularGlossiness.specularGlossinessTexture
      pending.push(parser.assignTexture(materialParams, 'glossinessMap', specGlossMapDef))
      pending.push(parser.assignTexture(materialParams, 'specularMap', specGlossMapDef))
    }

    return Promise.all(pending)
  }

  createMaterial(materialParams) {
    const material = new GLTFMeshStandardSGMaterial(materialParams)
    material.fog = true

    material.color = materialParams.color

    material.map = materialParams.map === undefined ? null : materialParams.map

    material.lightMap = null
    material.lightMapIntensity = 1.0

    material.aoMap = materialParams.aoMap === undefined ? null : materialParams.aoMap
    material.aoMapIntensity = 1.0

    material.emissive = materialParams.emissive
    material.emissiveIntensity = 1.0
    material.emissiveMap = materialParams.emissiveMap === undefined ? null : materialParams.emissiveMap

    material.bumpMap = materialParams.bumpMap === undefined ? null : materialParams.bumpMap
    material.bumpScale = 1

    material.normalMap = materialParams.normalMap === undefined ? null : materialParams.normalMap
    material.normalMapType = TangentSpaceNormalMap

    if (materialParams.normalScale) material.normalScale = materialParams.normalScale

    material.displacementMap = null
    material.displacementScale = 1
    material.displacementBias = 0

    material.specularMap = materialParams.specularMap === undefined ? null : materialParams.specularMap
    material.specular = materialParams.specular

    material.glossinessMap = materialParams.glossinessMap === undefined ? null : materialParams.glossinessMap
    material.glossiness = materialParams.glossiness

    material.alphaMap = null

    material.envMap = materialParams.envMap === undefined ? null : materialParams.envMap
    material.envMapIntensity = 1.0

    material.refractionRatio = 0.98

    return material
  }
}

/**
 * Mesh Quantization Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_mesh_quantization
 */
class GLTFMeshQuantizationExtension {
  constructor() {
    this.name = EXTENSIONS.KHR_MESH_QUANTIZATION
  }
}

/*********************************/
/********** INTERPOLATION ********/
/*********************************/

// Spline Interpolation
// Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#appendix-c-spline-interpolation
class GLTFCubicSplineInterpolant extends Interpolant {
  constructor(parameterPositions, sampleValues, sampleSize, resultBuffer) {
    super(parameterPositions, sampleValues, sampleSize, resultBuffer)
  }

  copySampleValue_(index) {
    // Copies a sample value to the result buffer. See description of glTF
    // CUBICSPLINE values layout in interpolate_() function below.

    const result = this.resultBuffer,
      values = this.sampleValues,
      valueSize = this.valueSize,
      offset = index * valueSize * 3 + valueSize

    for (let i = 0; i !== valueSize; i++) {
      result[i] = values[offset + i]
    }

    return result
  }
}

GLTFCubicSplineInterpolant.prototype.beforeStart_ = GLTFCubicSplineInterpolant.prototype.copySampleValue_

GLTFCubicSplineInterpolant.prototype.afterEnd_ = GLTFCubicSplineInterpolant.prototype.copySampleValue_

GLTFCubicSplineInterpolant.prototype.interpolate_ = function (i1, t0, t, t1) {
  const result = this.resultBuffer
  const values = this.sampleValues
  const stride = this.valueSize

  const stride2 = stride * 2
  const stride3 = stride * 3

  const td = t1 - t0

  const p = (t - t0) / td
  const pp = p * p
  const ppp = pp * p

  const offset1 = i1 * stride3
  const offset0 = offset1 - stride3

  const s2 = -2 * ppp + 3 * pp
  const s3 = ppp - pp
  const s0 = 1 - s2
  const s1 = s3 - pp + p

  // Layout of keyframe output values for CUBICSPLINE animations:
  //   [ inTangent_1, splineVertex_1, outTangent_1, inTangent_2, splineVertex_2, ... ]
  for (let i = 0; i !== stride; i++) {
    const p0 = values[offset0 + i + stride] // splineVertex_k
    const m0 = values[offset0 + i + stride2] * td // outTangent_k * (t_k+1 - t_k)
    const p1 = values[offset1 + i + stride] // splineVertex_k+1
    const m1 = values[offset1 + i] * td // inTangent_k+1 * (t_k+1 - t_k)

    result[i] = s0 * p0 + s1 * m0 + s2 * p1 + s3 * m1
  }

  return result
}

/*********************************/
/********** INTERNALS ************/
/*********************************/

/* CONSTANTS */

const WEBGL_CONSTANTS = {
  FLOAT: 5126,
  //FLOAT_MAT2: 35674,
  FLOAT_MAT3: 35675,
  FLOAT_MAT4: 35676,
  FLOAT_VEC2: 35664,
  FLOAT_VEC3: 35665,
  FLOAT_VEC4: 35666,
  LINEAR: 9729,
  REPEAT: 10497,
  SAMPLER_2D: 35678,
  POINTS: 0,
  LINES: 1,
  LINE_LOOP: 2,
  LINE_STRIP: 3,
  TRIANGLES: 4,
  TRIANGLE_STRIP: 5,
  TRIANGLE_FAN: 6,
  UNSIGNED_BYTE: 5121,
  UNSIGNED_SHORT: 5123
}

const WEBGL_COMPONENT_TYPES = {
  5120: Int8Array,
  5121: Uint8Array,
  5122: Int16Array,
  5123: Uint16Array,
  5125: Uint32Array,
  5126: Float32Array
}

const WEBGL_FILTERS = {
  9728: NearestFilter,
  9729: LinearFilter,
  9984: NearestMipmapNearestFilter,
  9985: LinearMipmapNearestFilter,
  9986: NearestMipmapLinearFilter,
  9987: LinearMipmapLinearFilter
}

const WEBGL_WRAPPINGS = {
  33071: ClampToEdgeWrapping,
  33648: MirroredRepeatWrapping,
  10497: RepeatWrapping
}

const WEBGL_TYPE_SIZES = {
  SCALAR: 1,
  VEC2: 2,
  VEC3: 3,
  VEC4: 4,
  MAT2: 4,
  MAT3: 9,
  MAT4: 16
}

const ATTRIBUTES = {
  POSITION: 'position',
  NORMAL: 'normal',
  TANGENT: 'tangent',
  TEXCOORD_0: 'uv',
  TEXCOORD_1: 'uv2',
  COLOR_0: 'color',
  WEIGHTS_0: 'skinWeight',
  JOINTS_0: 'skinIndex'
}

const PATH_PROPERTIES = {
  scale: 'scale',
  translation: 'position',
  rotation: 'quaternion',
  weights: 'morphTargetInfluences'
}

const INTERPOLATION = {
  CUBICSPLINE: undefined, // We use a custom interpolant (GLTFCubicSplineInterpolation) for CUBICSPLINE tracks. Each
  // keyframe track will be initialized with a default interpolation type, then modified.
  LINEAR: InterpolateLinear,
  STEP: InterpolateDiscrete
}

const ALPHA_MODES = {
  OPAQUE: 'OPAQUE',
  MASK: 'MASK',
  BLEND: 'BLEND'
}

/* UTILITY FUNCTIONS */

function resolveURL(url, path) {
  // Invalid URL
  if (typeof url !== 'string' || url === '') return ''

  // Host Relative URL
  if (/^https?:\/\//i.test(path) && /^\//.test(url)) {
    path = path.replace(/(^https?:\/\/[^\/]+).*/i, '$1')
  }

  // Absolute URL http://,https://,//
  if (/^(https?:)?\/\//i.test(url)) return url

  // Data URI
  if (/^data:.*,.*$/i.test(url)) return url

  // Blob URL
  if (/^blob:.*$/i.test(url)) return url

  // Relative URL
  return path + url
}

/**
 * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#default-material
 */
function createDefaultMaterial(cache) {
  if (cache['DefaultMaterial'] === undefined) {
    cache['DefaultMaterial'] = new MeshStandardMaterial({
      color: 0xffffff,
      emissive: 0x000000,
      metalness: 1,
      roughness: 1,
      transparent: false,
      depthTest: true,
      side: FrontSide
    })
  }

  return cache['DefaultMaterial']
}

function addUnknownExtensionsToUserData(knownExtensions, object, objectDef) {
  // Add unknown glTF extensions to an object's userData.

  for (const name in objectDef.extensions) {
    if (knownExtensions[name] === undefined) {
      object.userData.gltfExtensions = object.userData.gltfExtensions || {}
      object.userData.gltfExtensions[name] = objectDef.extensions[name]
    }
  }
}

/**
 * @param {Object3D|Material|BufferGeometry} object
 * @param {GLTF.definition} gltfDef
 */
function assignExtrasToUserData(object, gltfDef) {
  if (gltfDef.extras !== undefined) {
    if (typeof gltfDef.extras === 'object') {
      Object.assign(object.userData, gltfDef.extras)
    } else {
      console.warn('THREE.GLTFLoader: Ignoring primitive type .extras, ' + gltfDef.extras)
    }
  }
}

/**
 * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#morph-targets
 *
 * @param {BufferGeometry} geometry
 * @param {Array<GLTF.Target>} targets
 * @param {GLTFParser} parser
 * @return {Promise<BufferGeometry>}
 */
function addMorphTargets(geometry, targets, parser) {
  let hasMorphPosition = false
  let hasMorphNormal = false

  for (let i = 0, il = targets.length; i < il; i++) {
    const target = targets[i]

    if (target.POSITION !== undefined) hasMorphPosition = true
    if (target.NORMAL !== undefined) hasMorphNormal = true

    if (hasMorphPosition && hasMorphNormal) break
  }

  if (!hasMorphPosition && !hasMorphNormal) return Promise.resolve(geometry)

  const pendingPositionAccessors = []
  const pendingNormalAccessors = []

  for (let i = 0, il = targets.length; i < il; i++) {
    const target = targets[i]

    if (hasMorphPosition) {
      const pendingAccessor =
        target.POSITION !== undefined ? parser.getDependency('accessor', target.POSITION) : geometry.attributes.position

      pendingPositionAccessors.push(pendingAccessor)
    }

    if (hasMorphNormal) {
      const pendingAccessor =
        target.NORMAL !== undefined ? parser.getDependency('accessor', target.NORMAL) : geometry.attributes.normal

      pendingNormalAccessors.push(pendingAccessor)
    }
  }

  return Promise.all([Promise.all(pendingPositionAccessors), Promise.all(pendingNormalAccessors)]).then(
    function (accessors) {
      const morphPositions = accessors[0]
      const morphNormals = accessors[1]

      if (hasMorphPosition) geometry.morphAttributes.position = morphPositions
      if (hasMorphNormal) geometry.morphAttributes.normal = morphNormals
      geometry.morphTargetsRelative = true

      return geometry
    }
  )
}

/**
 * @param {Mesh} mesh
 * @param {GLTF.Mesh} meshDef
 */
function updateMorphTargets(mesh, meshDef) {
  mesh.updateMorphTargets()

  if (meshDef.weights !== undefined) {
    for (let i = 0, il = meshDef.weights.length; i < il; i++) {
      mesh.morphTargetInfluences[i] = meshDef.weights[i]
    }
  }

  // .extras has user-defined data, so check that .extras.targetNames is an array.
  if (meshDef.extras && Array.isArray(meshDef.extras.targetNames)) {
    const targetNames = meshDef.extras.targetNames

    if (mesh.morphTargetInfluences.length === targetNames.length) {
      mesh.morphTargetDictionary = {}

      for (let i = 0, il = targetNames.length; i < il; i++) {
        mesh.morphTargetDictionary[targetNames[i]] = i
      }
    } else {
      console.warn('THREE.GLTFLoader: Invalid extras.targetNames length. Ignoring names.')
    }
  }
}

function createPrimitiveKey(primitiveDef) {
  const dracoExtension = primitiveDef.extensions && primitiveDef.extensions[EXTENSIONS.KHR_DRACO_MESH_COMPRESSION]
  let geometryKey

  if (dracoExtension) {
    geometryKey =
      'draco:' +
      dracoExtension.bufferView +
      ':' +
      dracoExtension.indices +
      ':' +
      createAttributesKey(dracoExtension.attributes)
  } else {
    geometryKey = primitiveDef.indices + ':' + createAttributesKey(primitiveDef.attributes) + ':' + primitiveDef.mode
  }

  return geometryKey
}

function createAttributesKey(attributes) {
  let attributesKey = ''

  const keys = Object.keys(attributes).sort()

  for (let i = 0, il = keys.length; i < il; i++) {
    attributesKey += keys[i] + ':' + attributes[keys[i]] + ';'
  }

  return attributesKey
}

function getNormalizedComponentScale(constructor) {
  // Reference:
  // https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_mesh_quantization#encoding-quantized-data

  switch (constructor) {
    case Int8Array:
      return 1 / 127

    case Uint8Array:
      return 1 / 255

    case Int16Array:
      return 1 / 32767

    case Uint16Array:
      return 1 / 65535

    default:
      throw new Error('THREE.GLTFLoader: Unsupported normalized accessor component type.')
  }
}

/* GLTF PARSER */

class GLTFParser {
  constructor(json = {}, options = {}) {
    this.json = json
    this.extensions = {}
    this.plugins = {}
    this.options = options

    // loader object cache
    this.cache = new GLTFRegistry()

    // associations between Three.js objects and glTF elements
    this.associations = new Map()

    // BufferGeometry caching
    this.primitiveCache = {}

    // Object3D instance caches
    this.meshCache = { refs: {}, uses: {} }
    this.cameraCache = { refs: {}, uses: {} }
    this.lightCache = { refs: {}, uses: {} }

    this.textureCache = {}

    // Track node names, to ensure no duplicates
    this.nodeNamesUsed = {}

    // Use an ImageBitmapLoader if imageBitmaps are supported. Moves much of the
    // expensive work of uploading a texture to the GPU off the main thread.
    if (typeof createImageBitmap !== 'undefined' && /Firefox/.test(navigator.userAgent) === false) {
      this.textureLoader = new ImageBitmapLoader(this.options.manager)
    } else {
      this.textureLoader = new TextureLoader(this.options.manager)
    }

    this.textureLoader.setCrossOrigin(this.options.crossOrigin)
    this.textureLoader.setRequestHeader(this.options.requestHeader)

    this.fileLoader = new FileLoader(this.options.manager)
    this.fileLoader.setResponseType('arraybuffer')

    if (this.options.crossOrigin === 'use-credentials') {
      this.fileLoader.setWithCredentials(true)
    }
  }

  setExtensions(extensions) {
    this.extensions = extensions
  }

  setPlugins(plugins) {
    this.plugins = plugins
  }

  parse(onLoad, onError) {
    const parser = this
    const json = this.json
    const extensions = this.extensions

    // Clear the loader cache
    this.cache.removeAll()

    // Mark the special nodes/meshes in json for efficient parse
    this._invokeAll(function (ext) {
      return ext._markDefs && ext._markDefs()
    })

    Promise.all(
      this._invokeAll(function (ext) {
        return ext.beforeRoot && ext.beforeRoot()
      })
    )
      .then(function () {
        return Promise.all([
          parser.getDependencies('scene'),
          parser.getDependencies('animation'),
          parser.getDependencies('camera')
        ])
      })
      .then(function (dependencies) {
        const result = {
          scene: dependencies[0][json.scene || 0],
          scenes: dependencies[0],
          animations: dependencies[1],
          cameras: dependencies[2],
          asset: json.asset,
          parser: parser,
          userData: {}
        }

        addUnknownExtensionsToUserData(extensions, result, json)

        assignExtrasToUserData(result, json)

        Promise.all(
          parser._invokeAll(function (ext) {
            return ext.afterRoot && ext.afterRoot(result)
          })
        ).then(function () {
          onLoad(result)
        })
      })
      .catch(onError)
  }

  /**
   * Marks the special nodes/meshes in json for efficient parse.
   */
  _markDefs() {
    const nodeDefs = this.json.nodes || []
    const skinDefs = this.json.skins || []
    const meshDefs = this.json.meshes || []

    // Nothing in the node definition indicates whether it is a Bone or an
    // Object3D. Use the skins' joint references to mark bones.
    for (let skinIndex = 0, skinLength = skinDefs.length; skinIndex < skinLength; skinIndex++) {
      const joints = skinDefs[skinIndex].joints

      for (let i = 0, il = joints.length; i < il; i++) {
        nodeDefs[joints[i]].isBone = true
      }
    }

    // Iterate over all nodes, marking references to shared resources,
    // as well as skeleton joints.
    for (let nodeIndex = 0, nodeLength = nodeDefs.length; nodeIndex < nodeLength; nodeIndex++) {
      const nodeDef = nodeDefs[nodeIndex]

      if (nodeDef.mesh !== undefined) {
        this._addNodeRef(this.meshCache, nodeDef.mesh)

        // Nothing in the mesh definition indicates whether it is
        // a SkinnedMesh or Mesh. Use the node's mesh reference
        // to mark SkinnedMesh if node has skin.
        if (nodeDef.skin !== undefined) {
          meshDefs[nodeDef.mesh].isSkinnedMesh = true
        }
      }

      if (nodeDef.camera !== undefined) {
        this._addNodeRef(this.cameraCache, nodeDef.camera)
      }
    }
  }

  /**
   * Counts references to shared node / Object3D resources. These resources
   * can be reused, or "instantiated", at multiple nodes in the scene
   * hierarchy. Mesh, Camera, and Light instances are instantiated and must
   * be marked. Non-scenegraph resources (like Materials, Geometries, and
   * Textures) can be reused directly and are not marked here.
   *
   * Example: CesiumMilkTruck sample model reuses "Wheel" meshes.
   */
  _addNodeRef(cache, index) {
    if (index === undefined) return

    if (cache.refs[index] === undefined) {
      cache.refs[index] = cache.uses[index] = 0
    }

    cache.refs[index]++
  }

  /** Returns a reference to a shared resource, cloning it if necessary. */
  _getNodeRef(cache, index, object) {
    if (cache.refs[index] <= 1) return object

    const ref = object.clone()

    ref.name += '_instance_' + cache.uses[index]++

    return ref
  }

  _invokeOne(func) {
    const extensions = Object.values(this.plugins)
    extensions.push(this)

    for (let i = 0; i < extensions.length; i++) {
      const result = func(extensions[i])

      if (result) return result
    }

    return null
  }

  _invokeAll(func) {
    const extensions = Object.values(this.plugins)
    extensions.unshift(this)

    const pending = []

    for (let i = 0; i < extensions.length; i++) {
      const result = func(extensions[i])

      if (result) pending.push(result)
    }

    return pending
  }

  /**
   * Requests the specified dependency asynchronously, with caching.
   * @param {string} type
   * @param {number} index
   * @return {Promise<Object3D|Material|THREE.Texture|AnimationClip|ArrayBuffer|Object>}
   */
  getDependency(type, index) {
    const cacheKey = type + ':' + index
    let dependency = this.cache.get(cacheKey)

    if (!dependency) {
      switch (type) {
        case 'scene':
          dependency = this.loadScene(index)
          break

        case 'node':
          dependency = this.loadNode(index)
          break

        case 'mesh':
          dependency = this._invokeOne(function (ext) {
            return ext.loadMesh && ext.loadMesh(index)
          })
          break

        case 'accessor':
          dependency = this.loadAccessor(index)
          break

        case 'bufferView':
          dependency = this._invokeOne(function (ext) {
            return ext.loadBufferView && ext.loadBufferView(index)
          })
          break

        case 'buffer':
          dependency = this.loadBuffer(index)
          break

        case 'material':
          dependency = this._invokeOne(function (ext) {
            return ext.loadMaterial && ext.loadMaterial(index)
          })
          break

        case 'texture':
          dependency = this._invokeOne(function (ext) {
            return ext.loadTexture && ext.loadTexture(index)
          })
          break

        case 'skin':
          dependency = this.loadSkin(index)
          break

        case 'animation':
          dependency = this.loadAnimation(index)
          break

        case 'camera':
          dependency = this.loadCamera(index)
          break

        default:
          throw new Error('Unknown type: ' + type)
      }

      this.cache.add(cacheKey, dependency)
    }

    return dependency
  }

  /**
   * Requests all dependencies of the specified type asynchronously, with caching.
   * @param {string} type
   * @return {Promise<Array<Object>>}
   */
  getDependencies(type) {
    let dependencies = this.cache.get(type)

    if (!dependencies) {
      const parser = this
      const defs = this.json[type + (type === 'mesh' ? 'es' : 's')] || []

      dependencies = Promise.all(
        defs.map(function (def, index) {
          return parser.getDependency(type, index)
        })
      )

      this.cache.add(type, dependencies)
    }

    return dependencies
  }

  /**
   * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#buffers-and-buffer-views
   * @param {number} bufferIndex
   * @return {Promise<ArrayBuffer>}
   */
  loadBuffer(bufferIndex) {
    const bufferDef = this.json.buffers[bufferIndex]
    const loader = this.fileLoader

    if (bufferDef.type && bufferDef.type !== 'arraybuffer') {
      throw new Error('THREE.GLTFLoader: ' + bufferDef.type + ' buffer type is not supported.')
    }

    // If present, GLB container is required to be the first buffer.
    if (bufferDef.uri === undefined && bufferIndex === 0) {
      return Promise.resolve(this.extensions[EXTENSIONS.KHR_BINARY_GLTF].body)
    }

    const options = this.options

    return new Promise(function (resolve, reject) {
      loader.load(resolveURL(bufferDef.uri, options.path), resolve, undefined, function () {
        reject(new Error('THREE.GLTFLoader: Failed to load buffer "' + bufferDef.uri + '".'))
      })
    })
  }

  /**
   * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#buffers-and-buffer-views
   * @param {number} bufferViewIndex
   * @return {Promise<ArrayBuffer>}
   */
  loadBufferView(bufferViewIndex) {
    const bufferViewDef = this.json.bufferViews[bufferViewIndex]

    return this.getDependency('buffer', bufferViewDef.buffer).then(function (buffer) {
      const byteLength = bufferViewDef.byteLength || 0
      const byteOffset = bufferViewDef.byteOffset || 0
      return buffer.slice(byteOffset, byteOffset + byteLength)
    })
  }

  /**
   * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#accessors
   * @param {number} accessorIndex
   * @return {Promise<BufferAttribute|InterleavedBufferAttribute>}
   */
  loadAccessor(accessorIndex) {
    const parser = this
    const json = this.json

    const accessorDef = this.json.accessors[accessorIndex]

    if (accessorDef.bufferView === undefined && accessorDef.sparse === undefined) {
      // Ignore empty accessors, which may be used to declare runtime
      // information about attributes coming from another source (e.g. Draco
      // compression extension).
      return Promise.resolve(null)
    }

    const pendingBufferViews = []

    if (accessorDef.bufferView !== undefined) {
      pendingBufferViews.push(this.getDependency('bufferView', accessorDef.bufferView))
    } else {
      pendingBufferViews.push(null)
    }

    if (accessorDef.sparse !== undefined) {
      pendingBufferViews.push(this.getDependency('bufferView', accessorDef.sparse.indices.bufferView))
      pendingBufferViews.push(this.getDependency('bufferView', accessorDef.sparse.values.bufferView))
    }

    return Promise.all(pendingBufferViews).then(function (bufferViews) {
      const bufferView = bufferViews[0]

      const itemSize = WEBGL_TYPE_SIZES[accessorDef.type]
      const TypedArray = WEBGL_COMPONENT_TYPES[accessorDef.componentType]

      // For VEC3: itemSize is 3, elementBytes is 4, itemBytes is 12.
      const elementBytes = TypedArray.BYTES_PER_ELEMENT
      const itemBytes = elementBytes * itemSize
      const byteOffset = accessorDef.byteOffset || 0
      const byteStride =
        accessorDef.bufferView !== undefined ? json.bufferViews[accessorDef.bufferView].byteStride : undefined
      const normalized = accessorDef.normalized === true
      let array, bufferAttribute

      // The buffer is not interleaved if the stride is the item size in bytes.
      if (byteStride && byteStride !== itemBytes) {
        // Each "slice" of the buffer, as defined by 'count' elements of 'byteStride' bytes, gets its own InterleavedBuffer
        // This makes sure that IBA.count reflects accessor.count properly
        const ibSlice = Math.floor(byteOffset / byteStride)
        const ibCacheKey =
          'InterleavedBuffer:' +
          accessorDef.bufferView +
          ':' +
          accessorDef.componentType +
          ':' +
          ibSlice +
          ':' +
          accessorDef.count
        let ib = parser.cache.get(ibCacheKey)

        if (!ib) {
          array = new TypedArray(bufferView, ibSlice * byteStride, (accessorDef.count * byteStride) / elementBytes)

          // Integer parameters to IB/IBA are in array elements, not bytes.
          ib = new InterleavedBuffer(array, byteStride / elementBytes)

          parser.cache.add(ibCacheKey, ib)
        }

        bufferAttribute = new InterleavedBufferAttribute(
          ib,
          itemSize,
          (byteOffset % byteStride) / elementBytes,
          normalized
        )
      } else {
        if (bufferView === null) {
          array = new TypedArray(accessorDef.count * itemSize)
        } else {
          array = new TypedArray(bufferView, byteOffset, accessorDef.count * itemSize)
        }

        bufferAttribute = new BufferAttribute(array, itemSize, normalized)
      }

      // https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#sparse-accessors
      if (accessorDef.sparse !== undefined) {
        const itemSizeIndices = WEBGL_TYPE_SIZES.SCALAR
        const TypedArrayIndices = WEBGL_COMPONENT_TYPES[accessorDef.sparse.indices.componentType]

        const byteOffsetIndices = accessorDef.sparse.indices.byteOffset || 0
        const byteOffsetValues = accessorDef.sparse.values.byteOffset || 0

        const sparseIndices = new TypedArrayIndices(
          bufferViews[1],
          byteOffsetIndices,
          accessorDef.sparse.count * itemSizeIndices
        )
        const sparseValues = new TypedArray(bufferViews[2], byteOffsetValues, accessorDef.sparse.count * itemSize)

        if (bufferView !== null) {
          // Avoid modifying the original ArrayBuffer, if the bufferView wasn't initialized with zeroes.
          bufferAttribute = new BufferAttribute(
            bufferAttribute.array.slice(),
            bufferAttribute.itemSize,
            bufferAttribute.normalized
          )
        }

        for (let i = 0, il = sparseIndices.length; i < il; i++) {
          const index = sparseIndices[i]

          bufferAttribute.setX(index, sparseValues[i * itemSize])
          if (itemSize >= 2) bufferAttribute.setY(index, sparseValues[i * itemSize + 1])
          if (itemSize >= 3) bufferAttribute.setZ(index, sparseValues[i * itemSize + 2])
          if (itemSize >= 4) bufferAttribute.setW(index, sparseValues[i * itemSize + 3])
          if (itemSize >= 5) throw new Error('THREE.GLTFLoader: Unsupported itemSize in sparse BufferAttribute.')
        }
      }

      return bufferAttribute
    })
  }

  /**
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#textures
   * @param {number} textureIndex
   * @return {Promise<THREE.Texture>}
   */
  loadTexture(textureIndex) {
    return // MOD(yandeu)
    const json = this.json
    const options = this.options
    const textureDef = json.textures[textureIndex]
    const source = json.images[textureDef.source]

    let loader = this.textureLoader

    if (source.uri) {
      const handler = options.manager.getHandler(source.uri)
      if (handler !== null) loader = handler
    }

    return this.loadTextureImage(textureIndex, source, loader)
  }

  loadTextureImage(textureIndex, source, loader) {
    const parser = this
    const json = this.json
    const options = this.options

    const textureDef = json.textures[textureIndex]

    const cacheKey = (source.uri || source.bufferView) + ':' + textureDef.sampler

    if (this.textureCache[cacheKey]) {
      // See https://github.com/mrdoob/three.js/issues/21559.
      return this.textureCache[cacheKey]
    }

    const URL = self.URL || self.webkitURL

    let sourceURI = source.uri || ''
    let isObjectURL = false
    let hasAlpha = true

    const isJPEG = sourceURI.search(/\.jpe?g($|\?)/i) > 0 || sourceURI.search(/^data\:image\/jpeg/) === 0

    if (source.mimeType === 'image/jpeg' || isJPEG) hasAlpha = false

    if (source.bufferView !== undefined) {
      // Load binary image data from bufferView, if provided.

      sourceURI = parser.getDependency('bufferView', source.bufferView).then(function (bufferView) {
        if (source.mimeType === 'image/png') {
          // Inspect the PNG 'IHDR' chunk to determine whether the image could have an
          // alpha channel. This check is conservative — the image could have an alpha
          // channel with all values == 1, and the indexed type (colorType == 3) only
          // sometimes contains alpha.
          //
          // https://en.wikipedia.org/wiki/Portable_Network_Graphics#File_header
          const colorType = new DataView(bufferView, 25, 1).getUint8(0, false)
          hasAlpha = colorType === 6 || colorType === 4 || colorType === 3
        }

        isObjectURL = true
        const blob = new Blob([bufferView], { type: source.mimeType })
        sourceURI = URL.createObjectURL(blob)
        return sourceURI
      })
    } else if (source.uri === undefined) {
      throw new Error('THREE.GLTFLoader: Image ' + textureIndex + ' is missing URI and bufferView')
    }

    const promise = Promise.resolve(sourceURI)
      .then(function (sourceURI) {
        return new Promise(function (resolve, reject) {
          let onLoad = resolve

          if (loader.isImageBitmapLoader === true) {
            onLoad = function (imageBitmap) {
              const texture = new Texture(imageBitmap)
              texture.needsUpdate = true

              resolve(texture)
            }
          }

          loader.load(resolveURL(sourceURI, options.path), onLoad, undefined, reject)
        })
      })
      .then(function (texture) {
        // Clean up resources and configure Texture.

        if (isObjectURL === true) {
          URL.revokeObjectURL(sourceURI)
        }

        texture.flipY = false

        if (textureDef.name) texture.name = textureDef.name

        // When there is definitely no alpha channel in the texture, set RGBAFormat to save space.
        if (!hasAlpha) texture.format = RGBAFormat

        const samplers = json.samplers || {}
        const sampler = samplers[textureDef.sampler] || {}

        texture.magFilter = WEBGL_FILTERS[sampler.magFilter] || LinearFilter
        texture.minFilter = WEBGL_FILTERS[sampler.minFilter] || LinearMipmapLinearFilter
        texture.wrapS = WEBGL_WRAPPINGS[sampler.wrapS] || RepeatWrapping
        texture.wrapT = WEBGL_WRAPPINGS[sampler.wrapT] || RepeatWrapping

        parser.associations.set(texture, {
          type: 'textures',
          index: textureIndex
        })

        return texture
      })
      .catch(function () {
        console.error("THREE.GLTFLoader: Couldn't load texture", sourceURI)
        return null
      })

    this.textureCache[cacheKey] = promise

    return promise
  }

  /**
   * Asynchronously assigns a texture to the given material parameters.
   * @param {Object} materialParams
   * @param {string} mapName
   * @param {Object} mapDef
   * @return {Promise<Texture>}
   */
  assignTexture(materialParams, mapName, mapDef) {
    return // MOD(yandeu)
    const parser = this

    return this.getDependency('texture', mapDef.index).then(function (texture) {
      // Materials sample aoMap from UV set 1 and other maps from UV set 0 - this can't be configured
      // However, we will copy UV set 0 to UV set 1 on demand for aoMap
      if (mapDef.texCoord !== undefined && mapDef.texCoord != 0 && !(mapName === 'aoMap' && mapDef.texCoord == 1)) {
        console.warn(
          'THREE.GLTFLoader: Custom UV set ' + mapDef.texCoord + ' for texture ' + mapName + ' not yet supported.'
        )
      }

      if (parser.extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM]) {
        const transform =
          mapDef.extensions !== undefined ? mapDef.extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM] : undefined

        if (transform) {
          const gltfReference = parser.associations.get(texture)
          texture = parser.extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM].extendTexture(texture, transform)
          parser.associations.set(texture, gltfReference)
        }
      }

      materialParams[mapName] = texture

      return texture
    })
  }

  /**
   * Assigns final material to a Mesh, Line, or Points instance. The instance
   * already has a material (generated from the glTF material options alone)
   * but reuse of the same glTF material may require multiple threejs materials
   * to accommodate different primitive types, defines, etc. New materials will
   * be created if necessary, and reused from a cache.
   * @param  {Object3D} mesh Mesh, Line, or Points instance.
   */
  assignFinalMaterial(mesh) {
    const geometry = mesh.geometry
    let material = mesh.material

    const useVertexTangents = geometry.attributes.tangent !== undefined
    const useVertexColors = geometry.attributes.color !== undefined
    const useFlatShading = geometry.attributes.normal === undefined

    if (mesh.isPoints) {
      const cacheKey = 'PointsMaterial:' + material.uuid

      let pointsMaterial = this.cache.get(cacheKey)

      if (!pointsMaterial) {
        pointsMaterial = new PointsMaterial()
        Material.prototype.copy.call(pointsMaterial, material)
        pointsMaterial.color.copy(material.color)
        pointsMaterial.map = material.map
        pointsMaterial.sizeAttenuation = false // glTF spec says points should be 1px

        this.cache.add(cacheKey, pointsMaterial)
      }

      material = pointsMaterial
    } else if (mesh.isLine) {
      const cacheKey = 'LineBasicMaterial:' + material.uuid

      let lineMaterial = this.cache.get(cacheKey)

      if (!lineMaterial) {
        lineMaterial = new LineBasicMaterial()
        Material.prototype.copy.call(lineMaterial, material)
        lineMaterial.color.copy(material.color)

        this.cache.add(cacheKey, lineMaterial)
      }

      material = lineMaterial
    }

    // Clone the material if it will be modified
    if (useVertexTangents || useVertexColors || useFlatShading) {
      let cacheKey = 'ClonedMaterial:' + material.uuid + ':'

      if (material.isGLTFSpecularGlossinessMaterial) cacheKey += 'specular-glossiness:'
      if (useVertexTangents) cacheKey += 'vertex-tangents:'
      if (useVertexColors) cacheKey += 'vertex-colors:'
      if (useFlatShading) cacheKey += 'flat-shading:'

      let cachedMaterial = this.cache.get(cacheKey)

      if (!cachedMaterial) {
        cachedMaterial = material.clone()

        if (useVertexColors) cachedMaterial.vertexColors = true
        if (useFlatShading) cachedMaterial.flatShading = true

        if (useVertexTangents) {
          // https://github.com/mrdoob/three.js/issues/11438#issuecomment-507003995
          if (cachedMaterial.normalScale) cachedMaterial.normalScale.y *= -1
          if (cachedMaterial.clearcoatNormalScale) cachedMaterial.clearcoatNormalScale.y *= -1
        }

        this.cache.add(cacheKey, cachedMaterial)

        this.associations.set(cachedMaterial, this.associations.get(material))
      }

      material = cachedMaterial
    }

    // workarounds for mesh and geometry

    if (material.aoMap && geometry.attributes.uv2 === undefined && geometry.attributes.uv !== undefined) {
      geometry.setAttribute('uv2', geometry.attributes.uv)
    }

    mesh.material = material
  }

  getMaterialType(/* materialIndex */) {
    return MeshStandardMaterial
  }

  /**
   * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#materials
   * @param {number} materialIndex
   * @return {Promise<Material>}
   */
  loadMaterial(materialIndex) {
    const parser = this
    const json = this.json
    const extensions = this.extensions
    const materialDef = json.materials[materialIndex]

    let materialType
    const materialParams = {}
    const materialExtensions = materialDef.extensions || {}

    const pending = []

    if (materialExtensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS]) {
      const sgExtension = extensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS]
      materialType = sgExtension.getMaterialType()
      pending.push(sgExtension.extendParams(materialParams, materialDef, parser))
    } else if (materialExtensions[EXTENSIONS.KHR_MATERIALS_UNLIT]) {
      const kmuExtension = extensions[EXTENSIONS.KHR_MATERIALS_UNLIT]
      materialType = kmuExtension.getMaterialType()
      pending.push(kmuExtension.extendParams(materialParams, materialDef, parser))
    } else {
      // Specification:
      // https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#metallic-roughness-material

      const metallicRoughness = materialDef.pbrMetallicRoughness || {}

      materialParams.color = new Color(1.0, 1.0, 1.0)
      materialParams.opacity = 1.0

      if (Array.isArray(metallicRoughness.baseColorFactor)) {
        const array = metallicRoughness.baseColorFactor

        materialParams.color.fromArray(array)
        materialParams.opacity = array[3]
      }

      if (metallicRoughness.baseColorTexture !== undefined) {
        pending.push(parser.assignTexture(materialParams, 'map', metallicRoughness.baseColorTexture))
      }

      materialParams.metalness = metallicRoughness.metallicFactor !== undefined ? metallicRoughness.metallicFactor : 1.0
      materialParams.roughness =
        metallicRoughness.roughnessFactor !== undefined ? metallicRoughness.roughnessFactor : 1.0

      if (metallicRoughness.metallicRoughnessTexture !== undefined) {
        pending.push(parser.assignTexture(materialParams, 'metalnessMap', metallicRoughness.metallicRoughnessTexture))
        pending.push(parser.assignTexture(materialParams, 'roughnessMap', metallicRoughness.metallicRoughnessTexture))
      }

      materialType = this._invokeOne(function (ext) {
        return ext.getMaterialType && ext.getMaterialType(materialIndex)
      })

      pending.push(
        Promise.all(
          this._invokeAll(function (ext) {
            return ext.extendMaterialParams && ext.extendMaterialParams(materialIndex, materialParams)
          })
        )
      )
    }

    if (materialDef.doubleSided === true) {
      materialParams.side = DoubleSide
    }

    const alphaMode = materialDef.alphaMode || ALPHA_MODES.OPAQUE

    if (alphaMode === ALPHA_MODES.BLEND) {
      materialParams.transparent = true

      // See: https://github.com/mrdoob/three.js/issues/17706
      materialParams.depthWrite = false
    } else {
      materialParams.transparent = false

      if (alphaMode === ALPHA_MODES.MASK) {
        materialParams.alphaTest = materialDef.alphaCutoff !== undefined ? materialDef.alphaCutoff : 0.5
      }
    }

    if (materialDef.normalTexture !== undefined && materialType !== MeshBasicMaterial) {
      pending.push(parser.assignTexture(materialParams, 'normalMap', materialDef.normalTexture))

      // https://github.com/mrdoob/three.js/issues/11438#issuecomment-507003995
      materialParams.normalScale = new Vector2(1, -1)

      if (materialDef.normalTexture.scale !== undefined) {
        materialParams.normalScale.set(materialDef.normalTexture.scale, -materialDef.normalTexture.scale)
      }
    }

    if (materialDef.occlusionTexture !== undefined && materialType !== MeshBasicMaterial) {
      pending.push(parser.assignTexture(materialParams, 'aoMap', materialDef.occlusionTexture))

      if (materialDef.occlusionTexture.strength !== undefined) {
        materialParams.aoMapIntensity = materialDef.occlusionTexture.strength
      }
    }

    if (materialDef.emissiveFactor !== undefined && materialType !== MeshBasicMaterial) {
      materialParams.emissive = new Color().fromArray(materialDef.emissiveFactor)
    }

    if (materialDef.emissiveTexture !== undefined && materialType !== MeshBasicMaterial) {
      pending.push(parser.assignTexture(materialParams, 'emissiveMap', materialDef.emissiveTexture))
    }

    return Promise.all(pending).then(function () {
      let material

      if (materialType === GLTFMeshStandardSGMaterial) {
        material = extensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS].createMaterial(materialParams)
      } else {
        material = new materialType(materialParams)
      }

      if (materialDef.name) material.name = materialDef.name

      // baseColorTexture, emissiveTexture, and specularGlossinessTexture use sRGB encoding.
      // if (material.map) material.map.encoding = sRGBEncoding
      // if (material.emissiveMap) material.emissiveMap.encoding = sRGBEncoding

      assignExtrasToUserData(material, materialDef)

      parser.associations.set(material, { type: 'materials', index: materialIndex })

      if (materialDef.extensions) addUnknownExtensionsToUserData(extensions, material, materialDef)

      return material
    })
  }

  /** When Object3D instances are targeted by animation, they need unique names. */
  createUniqueName(originalName) {
    const sanitizedName = PropertyBinding.sanitizeNodeName(originalName || '')

    let name = sanitizedName

    for (let i = 1; this.nodeNamesUsed[name]; ++i) {
      name = sanitizedName + '_' + i
    }

    this.nodeNamesUsed[name] = true

    return name
  }

  /**
   * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#geometry
   *
   * Creates BufferGeometries from primitives.
   *
   * @param {Array<GLTF.Primitive>} primitives
   * @return {Promise<Array<BufferGeometry>>}
   */
  loadGeometries(primitives) {
    const parser = this
    const extensions = this.extensions
    const cache = this.primitiveCache

    function createDracoPrimitive(primitive) {
      return extensions[EXTENSIONS.KHR_DRACO_MESH_COMPRESSION]
        .decodePrimitive(primitive, parser)
        .then(function (geometry) {
          return addPrimitiveAttributes(geometry, primitive, parser)
        })
    }

    const pending = []

    for (let i = 0, il = primitives.length; i < il; i++) {
      const primitive = primitives[i]
      const cacheKey = createPrimitiveKey(primitive)

      // See if we've already created this geometry
      const cached = cache[cacheKey]

      if (cached) {
        // Use the cached geometry if it exists
        pending.push(cached.promise)
      } else {
        let geometryPromise

        if (primitive.extensions && primitive.extensions[EXTENSIONS.KHR_DRACO_MESH_COMPRESSION]) {
          // Use DRACO geometry if available
          geometryPromise = createDracoPrimitive(primitive)
        } else {
          // Otherwise create a new geometry
          geometryPromise = addPrimitiveAttributes(new BufferGeometry(), primitive, parser)
        }

        // Cache this geometry
        cache[cacheKey] = { primitive: primitive, promise: geometryPromise }

        pending.push(geometryPromise)
      }
    }

    return Promise.all(pending)
  }

  /**
   * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#meshes
   * @param {number} meshIndex
   * @return {Promise<Group|Mesh|SkinnedMesh>}
   */
  loadMesh(meshIndex) {
    const parser = this
    const json = this.json
    const extensions = this.extensions

    const meshDef = json.meshes[meshIndex]
    const primitives = meshDef.primitives

    const pending = []

    for (let i = 0, il = primitives.length; i < il; i++) {
      const material =
        primitives[i].material === undefined
          ? createDefaultMaterial(this.cache)
          : this.getDependency('material', primitives[i].material)

      pending.push(material)
    }

    pending.push(parser.loadGeometries(primitives))

    return Promise.all(pending).then(function (results) {
      const materials = results.slice(0, results.length - 1)
      const geometries = results[results.length - 1]

      const meshes = []

      for (let i = 0, il = geometries.length; i < il; i++) {
        const geometry = geometries[i]
        const primitive = primitives[i]

        // 1. create Mesh

        let mesh

        const material = materials[i]

        if (
          primitive.mode === WEBGL_CONSTANTS.TRIANGLES ||
          primitive.mode === WEBGL_CONSTANTS.TRIANGLE_STRIP ||
          primitive.mode === WEBGL_CONSTANTS.TRIANGLE_FAN ||
          primitive.mode === undefined
        ) {
          // .isSkinnedMesh isn't in glTF spec. See ._markDefs()
          mesh = meshDef.isSkinnedMesh === true ? new SkinnedMesh(geometry, material) : new Mesh(geometry, material)

          if (mesh.isSkinnedMesh === true && !mesh.geometry.attributes.skinWeight.normalized) {
            // we normalize floating point skin weight array to fix malformed assets (see #15319)
            // it's important to skip this for non-float32 data since normalizeSkinWeights assumes non-normalized inputs
            mesh.normalizeSkinWeights()
          }

          if (primitive.mode === WEBGL_CONSTANTS.TRIANGLE_STRIP) {
            mesh.geometry = toTrianglesDrawMode(mesh.geometry, TriangleStripDrawMode)
          } else if (primitive.mode === WEBGL_CONSTANTS.TRIANGLE_FAN) {
            mesh.geometry = toTrianglesDrawMode(mesh.geometry, TriangleFanDrawMode)
          }
        } else if (primitive.mode === WEBGL_CONSTANTS.LINES) {
          mesh = new LineSegments(geometry, material)
        } else if (primitive.mode === WEBGL_CONSTANTS.LINE_STRIP) {
          mesh = new Line(geometry, material)
        } else if (primitive.mode === WEBGL_CONSTANTS.LINE_LOOP) {
          mesh = new LineLoop(geometry, material)
        } else if (primitive.mode === WEBGL_CONSTANTS.POINTS) {
          mesh = new Points(geometry, material)
        } else {
          throw new Error('THREE.GLTFLoader: Primitive mode unsupported: ' + primitive.mode)
        }

        if (Object.keys(mesh.geometry.morphAttributes).length > 0) {
          updateMorphTargets(mesh, meshDef)
        }

        mesh.name = parser.createUniqueName(meshDef.name || 'mesh_' + meshIndex)

        assignExtrasToUserData(mesh, meshDef)

        if (primitive.extensions) addUnknownExtensionsToUserData(extensions, mesh, primitive)

        parser.assignFinalMaterial(mesh)

        meshes.push(mesh)
      }

      if (meshes.length === 1) {
        return meshes[0]
      }

      const group = new Group()

      for (let i = 0, il = meshes.length; i < il; i++) {
        group.add(meshes[i])
      }

      return group
    })
  }

  /**
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#cameras
   * @param {number} cameraIndex
   * @return {Promise<THREE.Camera>}
   */
  loadCamera(cameraIndex) {
    let camera
    const cameraDef = this.json.cameras[cameraIndex]
    const params = cameraDef[cameraDef.type]

    if (!params) {
      console.warn('THREE.GLTFLoader: Missing camera parameters.')
      return
    }

    if (cameraDef.type === 'perspective') {
      camera = new PerspectiveCamera(
        MathUtils.radToDeg(params.yfov),
        params.aspectRatio || 1,
        params.znear || 1,
        params.zfar || 2e6
      )
    } else if (cameraDef.type === 'orthographic') {
      camera = new OrthographicCamera(-params.xmag, params.xmag, params.ymag, -params.ymag, params.znear, params.zfar)
    }

    if (cameraDef.name) camera.name = this.createUniqueName(cameraDef.name)

    assignExtrasToUserData(camera, cameraDef)

    return Promise.resolve(camera)
  }

  /**
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#skins
   * @param {number} skinIndex
   * @return {Promise<Object>}
   */
  loadSkin(skinIndex) {
    const skinDef = this.json.skins[skinIndex]

    const skinEntry = { joints: skinDef.joints }

    if (skinDef.inverseBindMatrices === undefined) {
      return Promise.resolve(skinEntry)
    }

    return this.getDependency('accessor', skinDef.inverseBindMatrices).then(function (accessor) {
      skinEntry.inverseBindMatrices = accessor

      return skinEntry
    })
  }

  /**
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#animations
   * @param {number} animationIndex
   * @return {Promise<AnimationClip>}
   */
  loadAnimation(animationIndex) {
    const json = this.json

    const animationDef = json.animations[animationIndex]

    const pendingNodes = []
    const pendingInputAccessors = []
    const pendingOutputAccessors = []
    const pendingSamplers = []
    const pendingTargets = []

    for (let i = 0, il = animationDef.channels.length; i < il; i++) {
      const channel = animationDef.channels[i]
      const sampler = animationDef.samplers[channel.sampler]
      const target = channel.target
      const name = target.node !== undefined ? target.node : target.id // NOTE: target.id is deprecated.
      const input = animationDef.parameters !== undefined ? animationDef.parameters[sampler.input] : sampler.input
      const output = animationDef.parameters !== undefined ? animationDef.parameters[sampler.output] : sampler.output

      pendingNodes.push(this.getDependency('node', name))
      pendingInputAccessors.push(this.getDependency('accessor', input))
      pendingOutputAccessors.push(this.getDependency('accessor', output))
      pendingSamplers.push(sampler)
      pendingTargets.push(target)
    }

    return Promise.all([
      Promise.all(pendingNodes),
      Promise.all(pendingInputAccessors),
      Promise.all(pendingOutputAccessors),
      Promise.all(pendingSamplers),
      Promise.all(pendingTargets)
    ]).then(function (dependencies) {
      const nodes = dependencies[0]
      const inputAccessors = dependencies[1]
      const outputAccessors = dependencies[2]
      const samplers = dependencies[3]
      const targets = dependencies[4]

      const tracks = []

      for (let i = 0, il = nodes.length; i < il; i++) {
        const node = nodes[i]
        const inputAccessor = inputAccessors[i]
        const outputAccessor = outputAccessors[i]
        const sampler = samplers[i]
        const target = targets[i]

        if (node === undefined) continue

        node.updateMatrix()
        node.matrixAutoUpdate = true

        let TypedKeyframeTrack

        switch (PATH_PROPERTIES[target.path]) {
          case PATH_PROPERTIES.weights:
            TypedKeyframeTrack = NumberKeyframeTrack
            break

          case PATH_PROPERTIES.rotation:
            TypedKeyframeTrack = QuaternionKeyframeTrack
            break

          case PATH_PROPERTIES.position:
          case PATH_PROPERTIES.scale:
          default:
            TypedKeyframeTrack = VectorKeyframeTrack
            break
        }

        const targetName = node.name ? node.name : node.uuid

        const interpolation =
          sampler.interpolation !== undefined ? INTERPOLATION[sampler.interpolation] : InterpolateLinear

        const targetNames = []

        if (PATH_PROPERTIES[target.path] === PATH_PROPERTIES.weights) {
          // Node may be a Group (glTF mesh with several primitives) or a Mesh.
          node.traverse(function (object) {
            if (object.isMesh === true && object.morphTargetInfluences) {
              targetNames.push(object.name ? object.name : object.uuid)
            }
          })
        } else {
          targetNames.push(targetName)
        }

        let outputArray = outputAccessor.array

        if (outputAccessor.normalized) {
          const scale = getNormalizedComponentScale(outputArray.constructor)
          const scaled = new Float32Array(outputArray.length)

          for (let j = 0, jl = outputArray.length; j < jl; j++) {
            scaled[j] = outputArray[j] * scale
          }

          outputArray = scaled
        }

        for (let j = 0, jl = targetNames.length; j < jl; j++) {
          const track = new TypedKeyframeTrack(
            targetNames[j] + '.' + PATH_PROPERTIES[target.path],
            inputAccessor.array,
            outputArray,
            interpolation
          )

          // Override interpolation with custom factory method.
          if (sampler.interpolation === 'CUBICSPLINE') {
            track.createInterpolant = function InterpolantFactoryMethodGLTFCubicSpline(result) {
              // A CUBICSPLINE keyframe in glTF has three output values for each input value,
              // representing inTangent, splineVertex, and outTangent. As a result, track.getValueSize()
              // must be divided by three to get the interpolant's sampleSize argument.

              return new GLTFCubicSplineInterpolant(this.times, this.values, this.getValueSize() / 3, result)
            }

            // Mark as CUBICSPLINE. `track.getInterpolation()` doesn't support custom interpolants.
            track.createInterpolant.isInterpolantFactoryMethodGLTFCubicSpline = true
          }

          tracks.push(track)
        }
      }

      const name = animationDef.name ? animationDef.name : 'animation_' + animationIndex

      return new AnimationClip(name, undefined, tracks)
    })
  }

  createNodeMesh(nodeIndex) {
    const json = this.json
    const parser = this
    const nodeDef = json.nodes[nodeIndex]

    if (nodeDef.mesh === undefined) return null

    return parser.getDependency('mesh', nodeDef.mesh).then(function (mesh) {
      const node = parser._getNodeRef(parser.meshCache, nodeDef.mesh, mesh)

      // if weights are provided on the node, override weights on the mesh.
      if (nodeDef.weights !== undefined) {
        node.traverse(function (o) {
          if (!o.isMesh) return

          for (let i = 0, il = nodeDef.weights.length; i < il; i++) {
            o.morphTargetInfluences[i] = nodeDef.weights[i]
          }
        })
      }

      return node
    })
  }

  /**
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#nodes-and-hierarchy
   * @param {number} nodeIndex
   * @return {Promise<Object3D>}
   */
  loadNode(nodeIndex) {
    const json = this.json
    const extensions = this.extensions
    const parser = this

    const nodeDef = json.nodes[nodeIndex]

    // reserve node's name before its dependencies, so the root has the intended name.
    const nodeName = nodeDef.name ? parser.createUniqueName(nodeDef.name) : ''

    return (function () {
      const pending = []

      const meshPromise = parser._invokeOne(function (ext) {
        return ext.createNodeMesh && ext.createNodeMesh(nodeIndex)
      })

      if (meshPromise) {
        pending.push(meshPromise)
      }

      if (nodeDef.camera !== undefined) {
        pending.push(
          parser.getDependency('camera', nodeDef.camera).then(function (camera) {
            return parser._getNodeRef(parser.cameraCache, nodeDef.camera, camera)
          })
        )
      }

      parser
        ._invokeAll(function (ext) {
          return ext.createNodeAttachment && ext.createNodeAttachment(nodeIndex)
        })
        .forEach(function (promise) {
          pending.push(promise)
        })

      return Promise.all(pending)
    })().then(function (objects) {
      let node

      // .isBone isn't in glTF spec. See ._markDefs
      if (nodeDef.isBone === true) {
        node = new Bone()
      } else if (objects.length > 1) {
        node = new Group()
      } else if (objects.length === 1) {
        node = objects[0]
      } else {
        node = new Object3D()
      }

      if (node !== objects[0]) {
        for (let i = 0, il = objects.length; i < il; i++) {
          node.add(objects[i])
        }
      }

      if (nodeDef.name) {
        node.userData.name = nodeDef.name
        node.name = nodeName
      }

      assignExtrasToUserData(node, nodeDef)

      if (nodeDef.extensions) addUnknownExtensionsToUserData(extensions, node, nodeDef)

      if (nodeDef.matrix !== undefined) {
        const matrix = new Matrix4()
        matrix.fromArray(nodeDef.matrix)
        node.applyMatrix4(matrix)
      } else {
        if (nodeDef.translation !== undefined) {
          node.position.fromArray(nodeDef.translation)
        }

        if (nodeDef.rotation !== undefined) {
          node.quaternion.fromArray(nodeDef.rotation)
        }

        if (nodeDef.scale !== undefined) {
          node.scale.fromArray(nodeDef.scale)
        }
      }

      parser.associations.set(node, { type: 'nodes', index: nodeIndex })

      return node
    })
  }

  /**
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#scenes
   * @param {number} sceneIndex
   * @return {Promise<Group>}
   */
  loadScene(sceneIndex) {
    const json = this.json
    const extensions = this.extensions
    const sceneDef = this.json.scenes[sceneIndex]
    const parser = this

    // Loader returns Group, not Scene.
    // See: https://github.com/mrdoob/three.js/issues/18342#issuecomment-578981172
    const scene = new Group()
    if (sceneDef.name) scene.name = parser.createUniqueName(sceneDef.name)

    assignExtrasToUserData(scene, sceneDef)

    if (sceneDef.extensions) addUnknownExtensionsToUserData(extensions, scene, sceneDef)

    const nodeIds = sceneDef.nodes || []

    const pending = []

    for (let i = 0, il = nodeIds.length; i < il; i++) {
      pending.push(buildNodeHierachy(nodeIds[i], scene, json, parser))
    }

    return Promise.all(pending).then(function () {
      return scene
    })
  }
}

function buildNodeHierachy(nodeId, parentObject, json, parser) {
  const nodeDef = json.nodes[nodeId]

  return parser
    .getDependency('node', nodeId)
    .then(function (node) {
      if (nodeDef.skin === undefined) return node

      // build skeleton here as well

      let skinEntry

      return parser
        .getDependency('skin', nodeDef.skin)
        .then(function (skin) {
          skinEntry = skin

          const pendingJoints = []

          for (let i = 0, il = skinEntry.joints.length; i < il; i++) {
            pendingJoints.push(parser.getDependency('node', skinEntry.joints[i]))
          }

          return Promise.all(pendingJoints)
        })
        .then(function (jointNodes) {
          node.traverse(function (mesh) {
            if (!mesh.isMesh) return

            const bones = []
            const boneInverses = []

            for (let j = 0, jl = jointNodes.length; j < jl; j++) {
              const jointNode = jointNodes[j]

              if (jointNode) {
                bones.push(jointNode)

                const mat = new Matrix4()

                if (skinEntry.inverseBindMatrices !== undefined) {
                  mat.fromArray(skinEntry.inverseBindMatrices.array, j * 16)
                }

                boneInverses.push(mat)
              } else {
                console.warn('THREE.GLTFLoader: Joint "%s" could not be found.', skinEntry.joints[j])
              }
            }

            mesh.bind(new Skeleton(bones, boneInverses), mesh.matrixWorld)
          })

          return node
        })
    })
    .then(function (node) {
      // build node hierachy

      parentObject.add(node)

      const pending = []

      if (nodeDef.children) {
        const children = nodeDef.children

        for (let i = 0, il = children.length; i < il; i++) {
          const child = children[i]
          pending.push(buildNodeHierachy(child, node, json, parser))
        }
      }

      return Promise.all(pending)
    })
}

/**
 * @param {BufferGeometry} geometry
 * @param {GLTF.Primitive} primitiveDef
 * @param {GLTFParser} parser
 */
function computeBounds(geometry, primitiveDef, parser) {
  const attributes = primitiveDef.attributes

  const box = new Box3()

  if (attributes.POSITION !== undefined) {
    const accessor = parser.json.accessors[attributes.POSITION]

    const min = accessor.min
    const max = accessor.max

    // glTF requires 'min' and 'max', but VRM (which extends glTF) currently ignores that requirement.

    if (min !== undefined && max !== undefined) {
      box.set(new Vector3(min[0], min[1], min[2]), new Vector3(max[0], max[1], max[2]))

      if (accessor.normalized) {
        const boxScale = getNormalizedComponentScale(WEBGL_COMPONENT_TYPES[accessor.componentType])
        box.min.multiplyScalar(boxScale)
        box.max.multiplyScalar(boxScale)
      }
    } else {
      console.warn('THREE.GLTFLoader: Missing min/max properties for accessor POSITION.')

      return
    }
  } else {
    return
  }

  const targets = primitiveDef.targets

  if (targets !== undefined) {
    const maxDisplacement = new Vector3()
    const vector = new Vector3()

    for (let i = 0, il = targets.length; i < il; i++) {
      const target = targets[i]

      if (target.POSITION !== undefined) {
        const accessor = parser.json.accessors[target.POSITION]
        const min = accessor.min
        const max = accessor.max

        // glTF requires 'min' and 'max', but VRM (which extends glTF) currently ignores that requirement.

        if (min !== undefined && max !== undefined) {
          // we need to get max of absolute components because target weight is [-1,1]
          vector.setX(Math.max(Math.abs(min[0]), Math.abs(max[0])))
          vector.setY(Math.max(Math.abs(min[1]), Math.abs(max[1])))
          vector.setZ(Math.max(Math.abs(min[2]), Math.abs(max[2])))

          if (accessor.normalized) {
            const boxScale = getNormalizedComponentScale(WEBGL_COMPONENT_TYPES[accessor.componentType])
            vector.multiplyScalar(boxScale)
          }

          // Note: this assumes that the sum of all weights is at most 1. This isn't quite correct - it's more conservative
          // to assume that each target can have a max weight of 1. However, for some use cases - notably, when morph targets
          // are used to implement key-frame animations and as such only two are active at a time - this results in very large
          // boxes. So for now we make a box that's sometimes a touch too small but is hopefully mostly of reasonable size.
          maxDisplacement.max(vector)
        } else {
          console.warn('THREE.GLTFLoader: Missing min/max properties for accessor POSITION.')
        }
      }
    }

    // As per comment above this box isn't conservative, but has a reasonable size for a very large number of morph targets.
    box.expandByVector(maxDisplacement)
  }

  geometry.boundingBox = box

  const sphere = new Sphere()

  box.getCenter(sphere.center)
  sphere.radius = box.min.distanceTo(box.max) / 2

  geometry.boundingSphere = sphere
}

/**
 * @param {BufferGeometry} geometry
 * @param {GLTF.Primitive} primitiveDef
 * @param {GLTFParser} parser
 * @return {Promise<BufferGeometry>}
 */
function addPrimitiveAttributes(geometry, primitiveDef, parser) {
  const attributes = primitiveDef.attributes

  const pending = []

  function assignAttributeAccessor(accessorIndex, attributeName) {
    return parser.getDependency('accessor', accessorIndex).then(function (accessor) {
      geometry.setAttribute(attributeName, accessor)
    })
  }

  for (const gltfAttributeName in attributes) {
    const threeAttributeName = ATTRIBUTES[gltfAttributeName] || gltfAttributeName.toLowerCase()

    // Skip attributes already provided by e.g. Draco extension.
    if (threeAttributeName in geometry.attributes) continue

    pending.push(assignAttributeAccessor(attributes[gltfAttributeName], threeAttributeName))
  }

  if (primitiveDef.indices !== undefined && !geometry.index) {
    const accessor = parser.getDependency('accessor', primitiveDef.indices).then(function (accessor) {
      geometry.setIndex(accessor)
    })

    pending.push(accessor)
  }

  assignExtrasToUserData(geometry, primitiveDef)

  computeBounds(geometry, primitiveDef, parser)

  return Promise.all(pending).then(function () {
    return primitiveDef.targets !== undefined ? addMorphTargets(geometry, primitiveDef.targets, parser) : geometry
  })
}

/**
 * @param {BufferGeometry} geometry
 * @param {Number} drawMode
 * @return {BufferGeometry}
 */
function toTrianglesDrawMode(geometry, drawMode) {
  let index = geometry.getIndex()

  // generate index if not present

  if (index === null) {
    const indices = []

    const position = geometry.getAttribute('position')

    if (position !== undefined) {
      for (let i = 0; i < position.count; i++) {
        indices.push(i)
      }

      geometry.setIndex(indices)
      index = geometry.getIndex()
    } else {
      console.error('THREE.GLTFLoader.toTrianglesDrawMode(): Undefined position attribute. Processing not possible.')
      return geometry
    }
  }

  //

  const numberOfTriangles = index.count - 2
  const newIndices = []

  if (drawMode === TriangleFanDrawMode) {
    // gl.TRIANGLE_FAN

    for (let i = 1; i <= numberOfTriangles; i++) {
      newIndices.push(index.getX(0))
      newIndices.push(index.getX(i))
      newIndices.push(index.getX(i + 1))
    }
  } else {
    // gl.TRIANGLE_STRIP

    for (let i = 0; i < numberOfTriangles; i++) {
      if (i % 2 === 0) {
        newIndices.push(index.getX(i))
        newIndices.push(index.getX(i + 1))
        newIndices.push(index.getX(i + 2))
      } else {
        newIndices.push(index.getX(i + 2))
        newIndices.push(index.getX(i + 1))
        newIndices.push(index.getX(i))
      }
    }
  }

  if (newIndices.length / 3 !== numberOfTriangles) {
    console.error('THREE.GLTFLoader.toTrianglesDrawMode(): Unable to generate correct amount of triangles.')
  }

  // build final geometry

  const newGeometry = geometry.clone()
  newGeometry.setIndex(newIndices)

  return newGeometry
}

export { GLTFLoader }
